Sulfur-containing compounds, nitrogen-containing compounds, oxygen-containing compounds, and the like are contained in crude petroleum as impurities, and as to petroleum fractions obtained through a step such as distillation from the crude oil, the contents of these impurities are reduced by a step of bringing the fractions into contact with a catalyst having hydrogenation activity in the presence of hydrogen, the step being referred to as hydrotreatment. Desulfurization, for reducing the contents of the sulfur-containing compounds, is especially well known. Recently, in terms of reducing environmental load, there have been stricter demands for controlling or reducing the contents of impurities including sulfur-containing compounds in petroleum products, and a large number of so-called “sulfur-free” petroleum products are being manufactured.
After a hydrotreatment catalyst used for hydrotreatment of a petroleum fraction is used for a certain period of time, its activity is lowered due to the deposition of coke or sulfur components and the like, and replacement is therefore carried out. Especially due to the increase in demand for “sulfur-free” petroleum products, a greater hydrotreating capability is required in hydrotreating facilities for petroleum fractions such as kerosene, gas oil and vacuum gas oil, which increases the frequency of catalyst replacement, resulting in increased catalyst costs and a greater amount of waste catalyst.
As a countermeasure, a regenerated catalyst regenerated from a spent hydrotreatment catalyst is partially used in these facilities (For example, see Patent Literatures 1 and 2).